Rear projection screens used in rear-projection televisions etc. have ordinarily a constitution of two superposed lens sheets. Specifically, they comprise a Fresnel lens sheet and a lenticular lens sheet so aligned that the former is on the side of a light source while the latter is on the side of a viewer, wherein the Fresnel lens sheet has the function of focusing rays of image light from a CRT (Cathode Ray Tube) or those having passed through a liquid-crystal system thereby making them fall within a range of predetermined angles, while the lenticular lens sheet has the function of again diffusing the rays of image light having passed through the Fresnel lens sheet, thereby making them fall within a range of suitably broadened angles.
FIG. 4 shows a schematic perspective view of a rear-projection screen. As shown in FIG. 4, a rear-projection screen comprises basically a Fresnel lens sheet 2 and a lenticular lens sheet 1. In some cases there is also provided a translucent sheet 3, called a front plate, on the light exit surface of the lenticular lens sheet 1. Such a translucent sheet 3 is disclosed for instance in Japanese Unexamined Patent Application Publication Nos. H8-22077 or H7-307912. The translucent sheet 3 is provided for protecting the lenticular lens sheet and for obtaining a surface luminance similar to that of ordinary CRT televisions.
The Fresnel lens sheet 2 is constituted by a Fresnel lens, provided on the light exit side, that comprises equally spaced concentric fine-pitch lenses.
The lenticular lens sheet 1 is constituted by a translucent substrate wherein are formed a plurality of lenticular lenses 11 on the side receiving the incident image light. The other surface of the lenticular lens sheet 1, through which the image light exits, is generally formed so as to have thereon condensing sections 12, in the shape of a convex lens, which condense the image light from the lenticular lenses 11. The condensing sections 12 are lenticulated so as to improve their ability to diffuse the rays of image light in the horizontal direction. In particularly, when the lenticular lens sheet 1 is used in combination with three-tube CRT light sources, the condensing sections 12 must be indispensably lenticulated so as to correct the 3-color color shift. The non-condensing sections 13 (sections other than the condensing sections 12), in which the image light from the lenticular lenses 11 formed on the surface that receives the image light are not condensed, are ridged with side faces and tops parallel to the lenticular lens sheet 1. The tops of the ridges and the sides of each ridge adjacent to its top (the upper sides thereof) are all coated with an external light-absorbing layer 14 of black pigments etc., applied through roll coating, screen printing, transfer printing or the like, to form ridged external light-absorbing sections. Thus, the lenticular lens sheet 1 reduces, among the external light incident on the lenticular lens sheet 1, the light reflected through the light exit surface back toward the viewer, thereby increasing image contrast.
FIG. 5 is an enlarged-cross section of a conventional lenticular lens sheet 1. As shown in the figure, the non-condensing sections 13 comprise sides 13a, 13b and tops 13c. Herein external light-absorbing sections are formed by an external light-absorbing layer 14 provided on the tops 13c and on part of the sides 13a, 13b. In order to achieve effectively a further contrast increase, Japanese Unexamined Utility Model Application Publication No. S59-87042 proposes for instance providing an external light-absorbing layer 14 on the tops 13 and on the entirety of the sides 13a, 13b. 
However, the sides of the external light-absorbing sections in conventional lenticular lens sheets rise very steeply, which is problematic in that part of the light exiting from the condensing sections hits against the shoulders of the light-absorbing sections, thereby narrowing the viewing angle.
The tops of the conventional lenticular lens sheets have also the drawback of being perpendicular to the viewer, which increases the amount of external light reflected back to the viewer, resulting thus in a worse contrast.
In order to solve the above problems, an object of the present invention is to provide a wide viewing-angle lenticular lens sheet and manufacturing method for same.
Another object of the present invention is to provide a high-contrast lenticular lens sheet and manufacturing method for same.